A mutual team of researchers from the Centre of Excellence EcolChange and external partners revealed the important link between microbes, drying peatlands and climate warming, recently published in Nature Communications (https://rdcu.be/cJaZ8). Read their press release:
guest editors: Jaan Pärn, Mikk Espenberg, Ülo Mander
N2O (nitrous oxide), a dangerous greenhouse gas, warms the climate and destroys the stratospheric ozone layer. Nitrous oxide is an intermediate and by-product of several processes of the nitrous cycle conducted by soil microbes. Undisturbed (wet) peatlands do not lose much N2O but drained peatlands are substantial sources of nitrous oxide. A global study of peatlands led by geographers and microbiologists of the University of Tartu, Estonia identified the microbes in relation to the nitrous oxide emissions in different peatland environments.
Genetic analysis of soil samples from all major peatland regions and types of the world revealed that high nitrous-oxide emissions are associated with several microbial groups. Among those, richness of nitrifier archaea and bacteria, denitrifiers and ammonifiers (DNRA) emerged as important. The high nitrous-oxide producing peatlands showed a high abundance of all those microbial groups. Therefore, the more nitrous-oxide producing microbial groups are present in the soil, the more nitrous oxide the peatland emits.
Nitrous oxide is a nitrogen compound and thus part of the nitrous cycle. Nitrification is a process where microbes consume ammonium (NH4) and dissolved oxygen (O2) from the soil, and produce nitrous oxide and eventually nitrate (NO3). This study distinguished between nitrifier bacteria and archaea. The latter are a more ancient group that thrives in more extreme environments. Nitrifier archaea showed the most significant correlation with nitrous oxide emissions among the microbes. The study found abundant nitrifiers both in the dry and wet peatlands. This is a sure sign of climate change that has temporarily drawn down the water table and introduced oxygen in the wet peatlands.
Denitrification is a process where microbes, in the absence of dissolved oxygen, consume the oxygen from nitrate, and produce nitrous oxide and eventually inert N2 nitrogen. The study found abundant denitrifiers both in the wet and dry peatlands. This shows that even the driest of peatlands experience seasonal flood or even have permanently wet aggregates.
In conclusion, the results show complex mechanisms behind the nitrous oxide pollution. This calls for global attention. Microbes react rapidly to environmental change. It is difficult to stop them from producing nitrous oxide from highly available soil nitrogen compounds at favourable environmental conditions. Wise use of nitrogen fertilisers is one way to address the issue. It is equally important to combat climate change, especially climatic drying and manmade drainage of peatlands.